This invention relates to a method of forming a diode for integration with a semiconductor device and a method of forming a transistor device having an integrated diode.
The use of a diode integrated with a semiconductor device, such as a power MOSFET device, as an integrated temperature sensor is well known. For example, the forward voltage of the diode is proportional to the temperature of the diode and so by monitoring the forward voltage across a diode integrated with a power device, the temperature of the power device can be monitored which is useful, for example, when tracking the device""s temperature overshoot and subsequent shutdown.
Typically, an integrated diode is formed by doping a polysilicon layer with P-type and N-type dopants so as to form the diode""s PIN junction. Although some of the process steps of forming such a polysilicon diode can be combined with the other processing steps for the semiconductor device, the known techniques all suffer from the disadvantage of requiring some additional process steps, e.g. additional masking steps for the P-type and N-type implant, and additional P-type and N-type implant steps, to create the diode. Additional process steps increase the complexity and cost of manufacture and provide additional opportunity for defects, which reduce the overall yield from such processes and reliability of the final product.